Microcomputer for controlling ultrasonic motor, and method for controlling ultrasonic motor

ABSTRACT

A microcomputer that outputs a pulse signal controlling an ultrasonic motor includes a digital/analog, D/A, conversion set register that stores a D/A conversion set value setting an amplitude value of the pulse signal, a D/A converter that generates the amplitude value based on the D/A conversion set value, a first compare register that stores a first compare register value setting a frequency of the pulse signal, a second compare register that stores a second compare register value setting a duty ratio of the pulse signal, a counter that outputs a count value, a first comparator that compares the first compare register value with the count value to generate a first comparison result signal, and a second comparator that compares the second compare register value with the count value to generate a second comparison result signal.

INCORPORATION BY REFERENCE

The present application is a Continuation Application of U.S. patentapplication Ser. No. 12/457,897, filed on Jun. 24, 2009, which is basedupon and claims the benefit of priority from Japanese Patent ApplicationNo. 2008-166165 which was filed on Jun. 25, 2008, the disclosure ofwhich is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a microcomputer for controlling anultrasonic motor and to a method for controlling the ultrasonic motor.

2. Description of Related Art

There is a known ultrasonic motor having a stator that has apiezoelectric body and a moving body that performs rotational movement.In the ultrasonic motor, a traveling wave is generated on a stator whichis in turn excited by applying a control signal having a frequency in anultrasonic frequency band (20 kHz or higher), to the piezoelectric body.The ultrasonic motor transmits mechanical energy generated by ellipticmovement that occurs at respective points on the excited stator to themoving body to rotate the moving body so as to produce power.

The ultrasonic motor controls the rotation speed of the moving body byusing the frequency of the control signal applied to the piezoelectricbody. However, ultrasonic motors largely vary from one another in theircharacteristics. Accordingly, the rotation speed obtained at aparticular frequency varies among the ultrasonic motors, and theultrasonic motors, therefore, need to be controlled individually. Thetechnique shown below is disclosed as a technique controlling theultrasonic motor.

JP-A-2003-153558 discloses an oscillatory wave motor drive controldevice that applies an alternative sine wave with low distortion to thepiezoelectric body so that partial wear-and-tear (i.e., damage) lesslikely to occur on the stator, and an oscillatory wave motor having alonger service life can be realized. The oscillatory wave motor drivecontrol device of JP-A-2003-153558 is a drive control device for anoscillatory wave motor that excites an electro-mechanical energyconversion element to obtain a driving force by applying a frequencysignal to the electro-mechanical energy conversion element, whichincludes: an encoder for detecting a working speed of the oscillatorywave motor; a speed difference detecting unit for outputting a speeddifference signal by calculating a speed difference between the workingspeed detected by the encoder and a target speed of the oscillatory wavemotor; a frequency setting unit for setting a frequencyincrease/decrease amount based on the speed difference signal; areference voltage unit for generating a reference voltage correspondingto the target speed; a voltage detecting unit for detecting a voltage ofthe frequency signal applied to the oscillatory wave motor; a comparingunit for outputting a voltage difference signal by comparing thereference voltage generated by the reference voltage unit and thevoltage detected by the voltage detecting unit; a sine wave transmittingunit for transmitting a sine wave signal whose frequency is obtained bycalculating the frequency corresponding to the target speed and finelyadjusting the frequency based on the frequency increase/decrease amountset by the frequency setting unit and whose amplitude is determinedbased on the voltage difference signal output from the comparing unit; adriving signal generator for generating a plurality of sine wave drivingsignals of different phases based on the sine wave signal output fromthe sine wave transmitting unit; and a motor driving circuit forapplying periodic signals to the oscillatory wave motor based on theplurality of sine wave driving signals output from the driving signalgenerator.

SUMMARY

However, the present inventor has recognized the following point.Namely, the oscillatory wave motor drive control device ofJP-A-2003-153558 intends to optimize the characteristics of theultrasonic motor (i.e., oscillator motor) by controlling the frequencyand amplitude of a frequency signal to be input to the motor. Since theoscillatory wave motor drive control device of JP-A-2003-153558 isformed by many fixed circuits, however, it has low accuracy in thecontrol due to variation in the characteristics of the individualcircuits.

An exemplary feature of the present invention is to provide anultrasonic motor control device that is capable of adjusting thecharacteristics in a wider scope.

The present invention seeks to solve one or more of the above problems,or to improve upon those problems at least in part.

In one exemplary embodiment, a microcomputer that controls an ultrasonicmotor includes a storage unit that stores a compare register value, anda digital/analog (D/A) conversion set value, a D/A converter thatgenerates an amplitude control signal with an amplitude valuecorresponding to the D/A conversion set value, a timer that generates apulse width modulation (PWM) signal with a frequency corresponding tothe compare register value, a central processing unit (CPU) that readsthe D/A conversion set value, and the compare register value from thestorage unit, and that sets the D/A conversion set value and the compareregister value to the D/A converter and the timer, respectively, and anoutput circuit that generates the control signal with the amplitude ofthe amplitude control signal, and the frequency of the PWM signal, inresponse to the amplitude control signal and the PWM signal. The compareregister value is provided for determining a frequency of the controlsignal corresponding to a target rotation speed that is targeted by theultrasonic motor. The D/A conversion set value is provided fordetermining an amplitude of the control signal corresponding to thetarget rotation speed that is targeted by the ultrasonic motor.

In another exemplary embodiment, a microcompter that controls anultrasonic motor includes a storage unit that stores a compare registervalue, and a digital/analog (D/A) conversion set value, a D/A converterthat generates a amplitude control signal with an amplitude valuecorresponding to the D/A conversion set value, a timer that generates apulse width modulation (PWM) signal with a frequency corresponding tothe compare register value, a setting unit that reads the D/A conversionset value, and the compare register value from the storage unit, andthat sets the D/A conversion set value and the compare register value tothe D/A converter and the timer, respectively, and an output circuitthat generates the control signal with the amplitude of the amplitudecontrol signal, and the frequency of the PWM signal, in response to theamplitude control signal and the PWM signal. The compare register valueis provided for determining a frequency of the control signalcorresponding to a target rotation speed that is targeted by theultrasonic motor. The D/A conversion set value is provided fordetermining an amplitude of the control signal corresponding to thetarget rotation speed that is targeted by the ultrasonic motor.

In yet another exemplary embodiment, a method that is provided forcontrolling an ultrasonic motor by using a microcomputer includesproviding a digital/analog (D/A) conversion set value for determining anamplitude of a control signal corresponding to a target rotation speedthat is targeted by the ultrasonic or, providing a compare registervalue for determining a frequency of the control signal corresponding toa target rotation speed that is targeted by the ultrasonic motor,generating an amplitude control signal with an amplitude valuecorresponding to the D/A conversion set value, generating a pulse widthmodulation (PWM) signal with a frequency corresponding to the compareregister value, and generating the control signal with the amplitudevalue of the amplitude control signal, and the frequency of the PWMsignal, in response to the amplitude control signal and the PWM signal.

As mentioned above, an exemplary feature of the present invention is toprovide an ultrasonic motor control device that is capable of adjustingthe characteristics in a wider scope.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other purposes, advantages and features of the presentinvention will become more apparent from the following description ofcertain exemplary embodiments taken in conjunction with the accompanyingdrawings in which:

FIG. 1 is a block diagram showing the configuration of an ultrasonicmotor control device of a first exemplary embodiment;

FIG. 2 is a block diagram showing a microcomputer 1 in further detail inthe configuration of the ultrasonic motor control device of the firstexemplary embodiment;

FIG. 3 is a diagram showing an example of the configuration of an outputcircuit 161;

FIG. 4A is a timing chart showing an example of an operation of a timer151;

FIG. 4B is a timing chart showing an example of an operation of a timer151;

FIG. 4C is a timing chart showing an example of an operation of anoutput circuit 161;

FIG. 5 is a diagram for describing correction of control signalcharacteristics for an ultrasonic motor 3;

FIG. 6 is a diagram for describing the correction of the control signalcharacteristics for the ultrasonic motor 3;

FIG. 7 is an operation flow of the ultrasonic motor control deviceaccording to the first exemplary embodiment;

FIG. 8 is a block diagram showing a configuration of the ultrasonicmotor control device of a second exemplary embodiment; and

FIG. 9 is a block diagram showing an example of installing theultrasonic motor control device of the invention in a product 200.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The invention will now be described herein with reference toillustrative exemplary embodiments. Those skilled in the art willrecognize that many alternative embodiments can be accomplished usingthe knowledge of the present invention, and that the invention is notlimited to the exemplary embodiments illustrated for explanatorypurposes.

First Exemplar Embodiment [Description of the Configuration]

First, the configuration of the first exemplary embodiment will bedescribed with reference to FIG. 1 to FIG. 6. FIG. 1 is a block diagramshowing the configuration of the ultrasonic motor control device of thefirst exemplary embodiment. The ultrasonic motor control device of thefirst exemplary embodiment includes a microcomputer 1, a transformer 2,an ultrasonic motor 3, and an encoder 4.

First, the ultrasonic motor 3 will be described. The ultrasonic motor 3has a stator that has a piezoelectric body to which a control signal isinput and a moving body that performs rotational movement. Theultrasonic motor 3 excites the stator with a control signal that hasbeen input to the piezoelectric body and transmits the mechanical energyof the stator to a rotor to rotate the rotor. Since the ultrasonic motor3 is configured with the conventional art, detailed description thereofwill be omitted. In the first exemplary embodiment, the ultrasonic motor3 is controlled by using two-phase control signals having a phasedifference of 90 degrees. For that reason, the ultrasonic motor 3 of thefirst exemplary embodiment has two stators, each of which has thepiezoelectric body. The ultrasonic motor 3 receives the control signalfrom the transformer 2. Note that the control signal is not limited tobeing a two-phase control signal.

Next, the encoder 4 will be described. The encoder 4 detects therotation direction at the present time (hereinafter, the “currentrotation direction”) and the rotation speed (rpm) at the present time(hereinafter, the “current rotation speed”). The encoder 4 encodes thecurrent rotation direction and the current rotation speed of theultrasonic motor 3. The encoder 4 outputs the encoded current rotationdirection and current rotation speed to an up-down counter 17 of themicrocomputer 1 (described later). Since the encoder 4 is configuredwith the conventional art, detailed description thereof will be omitted.

Next, the transformer 2 will be described. The transformer 2 boosts thevoltage of the control signal input from the microcomputer 1. Thetransformer 2 outputs the control signal whose voltage has been boostedto the ultrasonic motor 3. Since the transformer 2 is configured withthe conventional art, detailed description thereof will be omitted.

Next, the microcomputer 1 will be described. FIG. 2 is a block diagramshowing the microcomputer 1 in further detail in the configuration ofthe ultrasonic motor control device of the first exemplary embodiment.The microcomputer 1 outputs the control signal for the ultrasonic motor3. The microcomputer 1 receives a drive command from outside (notshown). The microcomputer 1 generates the control signal for theultrasonic motor 3 based on the rotation direction targeted by theultrasonic motor 3 (hereinafter, “target rotation direction”) and therotation speed targeted by the ultrasonic motor 3 (hereinafter, “targetrotation speed”) that are commanded by the drive command. Themicrocomputer 1 receives inputs of the encoded current rotationdirection and current rotation speed from the encoder 4. Themicrocomputer 1 corrects the characteristics of the control signal basedon differences between the current rotation direction and the targetrotation direction and between the current rotation speed and the targetrotation speed. The microcomputer 1 outputs the control signal to thetransformer 2.

The microcomputer 1 has a central processing unit (CPU) 11; a flashmemory 12; a random access memory (RAM) 13; digital/analog (D/A)converting units 141 and 142; timers 151 and 152; output circuits 161,162; an up-down counter 17; and an internal bus 18. The CPU 11, theflash memory 12, the RAM 13, the D/A converting units 141 and 142, thetimers 151 and 152, the output circuits 161, 162, and the up-downcounter 17 are respectively connected with the internal bus 18 so thatthey can send and receive data via the internal bus 18. Each of thecomponents is driven as the power supply (VDD) is input from outside. Inthe first exemplary embodiment, the microcomputer 1 has two sets of theD/A converting unit 141, the timer 151, and the output circuit 161. Thisis because the ultrasonic motor 3 has two sets of the piezoelectric bodyin the first exemplary embodiment, which requires two inputs of thecontrol signals. If the ultrasonic motor 3 has four sets of thepiezoelectric body, then four inputs of the control signals arerequired. In such a case, the microcomputer 1 has four sets the D/Aconverting unit 141, the timer 151, and the output circuit 161 with fouroutputs for the control signals. It should be noted that themicrocomputer 1 has the D/A converting unit 141, the timer 151, and theoutput circuit 161 as many as that of the piezoelectric body sets in theultrasonic motor 3 (i.e., the number of the inputs of the controlsignals).

First, the CPU 11 controls the microcomputer 1. The CPU 11 implementsthe functions of the microcomputer 1 by executing a control program thatis stored in the flash memory 12.

Now, the flash memory 12 stores the control program and data forimplementing the functions of the microcomputer 1. The flash memory maybe a non-volatile memory such as a read only memory (ROM) or the like.The flash memory 12 has a data storing unit 121, setting means 122, andcalculating means 123.

The data storing unit 121 stores a D/A conversion set value and acompare register value. The D/A conversion set value is data to be setto D/A conversion setting registers 1411 and 1412 in the D/A convertingunits 141 and 142 (described later). The D/A conversion set value isused for determining each amplitude value (voltage value) of amplitudecontrol signals that are output from D/A conversions 1412, 1422. Thecompare register value is data to be set to compare registers 1512,1513, 1522 and 1523 of the timers 151 and 152 (described later). Thecompare register value is used for determining output timing of each oflow level signals to be output from the compare registers 1512 and 1522and pulse width control signals to be output from the compare registers1513 and 1523.

Each of the D/A conversion set value and the compare register value hasa reference value (hereinafter, the “reference D/A conversion set value”and the “reference compare register value”) and a correction value(hereinafter, the “correction D/A conversion set value” and the“correction compare register value”). Hereinafter, the expression “D/Aconversion set value” includes the reference D/A conversion set valueand the correction D/A conversion set value, and the expression “compareregister value” includes the reference compare register value and thecorrection compare register value, unless described particularly.

The reference D/A conversion set value and the reference compareregister value are determined based on the characteristics of thereferential ultrasonic motor 3. The reference D/A conversion set valueand the reference compare register value respectively indicate thefrequency and the amplitude value of the control signal corresponding tothe target rotation speed and the target rotation direction of thereferential ultrasonic motor 3.

The reference D/A conversion set value and the reference compareregister value are determined based on the characteristics of thereferential ultrasonic motor 3 that are obtained from many kinds ofstatistical data. The reference D/A conversion set value and thereference compare register value are stored in the data storing unit 121in advance in association with the target rotation speed and the targetrotation direction and the frequency and the amplitude value thatcorrespond to the target rotation speed and the target rotationdirection, respectively.

On the other hand, the correction D/A conversion set value and thecorrection compare register value are correction values from thereference D/A conversion set value and the reference compare registervalue. The correction D/A conversion set value and the correctioncompare register value are calculated by the calculating means 123 inthe case in which the current rotation speed and the current rotationdirection that are the characteristics of the ultrasonic motor 3 do notmatch the target rotation speed and the target rotation direction whenthe ultrasonic motor 3 are driven with the reference D/A conversion setvalue and the reference compare register value. This means that thecorrection D/A conversion set value and the correction compare registervalue are the characteristics of the control signal corresponding to thetarget rotation speed and the target rotation direction of theultrasonic motor 3. When the correction D/A conversion set value and thecorrection compare register value are calculated by the calculatingmeans 123, they are stored in the data storing unit 121.

The setting means 122 sets the D/A conversion set values to the D/Aconversion setting registers 1411, 1421. The setting means 122 may be acontrol program by the CPU 11. The set means 122 sets the compareregister values to the compare registers 1512, 1513, 1522 and 1523. Thesetting means 122 determines the frequency to be set (hereinafter,“setting frequency”) and the amplitude value to be set (hereinafter,“setting amplitude value”) that are the characteristics of the controlsignal corresponding to the target rotation direction and the targetrotation speed from the data storing unit 121 of the flash memory 12.

The setting means 122 obtains the D/A conversion set valuescorresponding to the setting amplitude values of the control signalsfrom the data storage area 121 and sets them to the D/A conversionsetting registers 1411, 1421. Also, the setting means 122 obtains thecompare register values corresponding to the setting frequencies of thecontrol signals from the data storage area 122 and sets them to thecompare registers 1512, 1513, 1522 and 1523.

If the correction D/A conversion set value and the correction compareregister value corresponding to the target rotation direction and thetarget rotation speed are stored in the data storing unit 121 when thesetting means 122 is to obtain the D/A conversion set value and thecompare register value from the data storing unit 121, then the settingmeans 122 obtains the correction D/A conversion set value and thecorrection compare register value. This is because the correction D/Aconversion set value and the correction compare register value are datacorrected in accordance with the characteristics of the ultrasonic motor3 that is actually to be controlled, and more accurate control can,therefore, be realized. Since the data storing unit 121 is stored in theflash memory 12, the correction D/A conversion set value and thecorrection compare register value are kept even after the microcomputer1 is switched off. Accordingly, the setting means 122 can set moreproper setting data by using the correction D/A conversion set value andthe correction compare register value.

If the correction D/A conversion set value and the correction compareregister value corresponding to the target rotation direction and thetarget rotation speed are not stored in the data storing unit 121 whenthe setting means 122 is to obtain the D/A conversion set value and thecompare register value from the data storing unit 121, then the settingmeans 122 obtains the reference D/A conversion set value and thereference compare register value.

When the setting means 122 has set the D/A conversion set values and thecompare register values, the setting means 122 outputs the values of thetarget rotation speeds and target rotation directions to the calculatingmeans 123. In that occasion, the setting means 122 also outputs thesetting frequencies and the setting amplitude values to the calculatingmeans 123. Instead of the setting frequencies and the setting amplitudevalues, the setting means 122 may output the D/A conversion set valuesthat have been set to the D/A conversion setting registers 1411, 1421and the compare register values that have been set to the compareregisters 1512, 1513, 1522 and 1523.

The calculating means 123 calculates the correction D/A conversion setvalue and the correction compare register value. The calculating means123 may be a control program executed by the CPU 11. The calculatingmeans 123 obtains the current rotation peed and the current rotationdirection that have been output by the encoder 4 and stored in theup-down counter 17. The calculating means 123 also obtains the targetrotation speed and the target rotation direction from the setting means122. The calculating means 123 calculates a difference rotation speedbased on the current rotation speed and the target rotation speed.

The calculating means 123 calculates a difference rotation directionbased on the current rotation direction and the target rotationdirection. The calculating means 123 calculates a corrected frequency(hereinafter, the “correction frequency”) and the corrected amplitudevalue (hereinafter, the “correction amplitude value”) that are requiredfor obtaining the target rotation speed and the target rotationdirection based on the difference rotation speed and the differencerotation direction. Further, the calculating means 123 calculates thecorrection D/A conversion set value and the correction compare registervalue that are required for obtaining the target rotation speed and thetarget rotation direction. The calculating means 123 stores thecalculated correction D/A conversion set value and correction compareregister value to the data storing unit 121 of the flash memory 12 inassociation with the target rotation speed and the target rotationdirection, respectively. The calculation of the correction D/Aconversion set value and the correction compare register value by thecalculating means 123 is not limited to that described above.

The calculating means 123 compares the setting frequency with thecorrection frequency and the setting amplitude value with the correctionamplitude value, respectively. When there is no difference between thesetting amplitude value and the correction amplitude value and there isa difference between the setting frequency and the correction frequency,the calculating means 123 judges that the adjustment can be completed bycorrecting only the frequency. Conversely, when there are differencesbetween the setting amplitude value and the correction amplitude valueand between the setting frequency and the correction frequency, thecalculating means 123 judges that both the frequency and the amplitudevalue need to be adjusted. The calculating means 123 informs the settingmeans 122 of the judgment result.

Next, when the CPU 11 is to execute the control program stored in theflash memory 12, it temporarily stores the control program in the RAM13.

Next, the D/A converting unit 141 outputs the amplitude control signalbased on the D/A conversion set value. The D/A converting unit 141 hasthe D/A conversion setting register 1411 and the D/A conversion 1412.The D/A conversion set value is written in the D/A conversion settingregister 1411 by the setting means 122. The D/A conversion 1412 obtainsthe D/A conversion set value from the D/A conversion setting register1411 and calculates the amplitude control signal having the amplitudevalue (voltage value) corresponding to the D/A conversion set value.When the microcomputer 1 is an eight bit microcomputer, for example, theD/A conversion 1412 calculates the amplitude value (voltage value) ofthe amplitude control signal by “the output voltage=the analog referencevoltage×m/256”. That is, if the analog reference voltage is 3.0 V andthe D/A conversion set value set to the D/A conversion setting register1411 is “00001111b (15in decimal), the D/A conversion 1412 calculates“3.0×15/256≈0.18”. In that case, the D/A conversion 1412 outputs theamplitude control signal with the amplitude of the voltage value “0.18V” to the output circuit 1161. As such, the D/A conversion 1412 canchange the amplitude value (voltage value) of the amplitude controlsignal based on the D/A conversion set value that has been set to theD/A conversion setting register 1411. The amplitude value (voltagevalue) of the amplitude control signal that is output by the D/Aconversion 1412 is the amplitude of the control signal for theultrasonic motor 3 that is output by the output circuit 161. Thecalculation of the voltage value by the D/A conversion 1412 is notlimited to that described above.

The D/A converting unit 142 may be the same as the D/A converting unit141. That is, the D/A conversion set value is written in the D/Aconversion setting register 1421 by the setting means 122. The D/Aconversion 1422 calculates the amplitude value (voltage value) byobtaining the D/A conversion set value from the D/A conversion settingregister 1421 and outputs the amplitude control signal with theamplitude of the voltage value to the output circuit 162. The amplitudevalue (voltage value) of the amplitude control signal that is output bythe D/A conversion 1422 is the amplitude of the control signal for theultrasonic motor 3 that is output by the output circuit 162.

Next, the timer 151 outputs a pulse width modulation (PWM) signal basedon the compare register value. The timer 151 has a counter 1511, thecompare registers 1512 and 1513, and a control circuit 1514. The counter1511 keeps counting on a certain cycle and outputs the count value. Thecompare register values are written in the compare registers 1512 and1513 respectively by the setting means 122. Each of the compareregisters 1512 and 1513 compares the register value set thereto with thecount value that is output by the counter 1511.

When the compare register value set thereto matches the count value thatis output by the counter 1511, each of the compare registers 1512 and1513 outputs the signal to the counter 1511 and the control circuit1514. The control circuit 1514 outputs the PWM signal based on thesignal from the compare registers 1512 and 1513. The signal output fromthe compare register 1512 is the pulse width control signal to thecontrol circuit 1514 (the output a in FIG. 2). The signal output fromthe compare register 1513 is the low level signal to the control circuit1514 (the output b in FIG. 2). When the set value and the count value inthe compare register 1512 match, the counter 1511 resets the countvalue.

After performing the count reset to make the count value reset to “0”,the counter 1511 resumes the counting. That is, the counter 1511 repeatscounting from the count “0” to the value which is the same as that setas the compare register value in the compare register 1512. When thepulse width control signal is input, the control circuit 1514 outputs apredetermined high voltage level (hereinafter, “H output”). On the otherhand, when the low level signal is input, the control circuit 1514outputs a predetermined low voltage level (hereinafter, “L output”).That is, after the pulse width control signal is input, the controlcircuit 1519 keeps the “H output” until the low level signal is input.As such, the control circuit 1519 determines the cycle and pulse widthof the PWM signal according to the pulse width control signal from thecompare register 1512 and the low level signal from the compare register1513. Each of the compare registers 1512 and 1513 can change the outputtiming of the pulse width control signal and the low level signal by thecompare register value set thereto.

As can be understood from the above, the compare register value set tothe compare register 1512 and the compare register value set to thecompare register 1513 are different from each other, and the adjustmentneeds to be performed on the values respectively. The actual voltagelevels of the “H output” and the “L output” for the PWM signal aredetermined by the working voltage of the output circuit to which the PWMsignal is input. For that reason, the voltage level for the PWM signalis nut particularly limited in the first exemplary embodiment. The cycleand pulse width of the PWM signal that is output by the control circuit1514 make the frequency of the control signal of the ultrasonic motor 3that is output by the output circuit 161.

The timer 152 may be the same as the timer 151. That is, the compareregister value is written in the compare register 1522 by the settingmeans 122. When the compare register value and the count value in thecounter 1521 match, the compare register 1522 outputs the pulse widthcontrol signal (the output c in FIG. 2) to the control circuit 1524. Thecompare register value is written in the compare register 1523 by thesetting means 122. When the compare register value and the count valuein the counter 1521 match, the compare register 1523 outputs the lowlevel signal (the output d in FIG. 2) to the control circuit 1524. Thecontrol circuit 1524 outputs the PWM signal to the output circuit 162based on the low level signal and the pulse width control signal. Thecycle and pulse width of the PWM signal that is output by the controlcircuit 1524 make the frequency of the control signal of the ultrasonicmotor 3 that is output by the output circuit 162.

Next, the output circuit 161 outputs the control signal for theultrasonic motor 3 based on the PWM signal that is output by the controlcircuit 1514 and the amplitude control signal that is output by the D/Aconversion 1412. FIG. 3 shows an example of the configuration of theoutput circuit 161. FIG. 3 shows an example of a case in which theoutput circuit 161 is configured by an Nch open drain.

In the output circuit of the FIG. 3, the output of the control circuit1514 is connected with a gate electrode of the Nch open drain. Theoutput of the D/A conversion 1412 is connected with the drain electrodeof the Nch open drain via a pull-up resistor 8100 and makes the outputto the transformer 2. A source electrode is grounded (hereinafter,“GND”). That is, it is configured that the PWM signal output by thecontrol circuit 1514 plays the role of a switch for outputting theamplitude control signal from the D/A conversion 1412 to the transformer2.

When the PWM signal from the control circuit 1514 is the “H output”, theoutput circuit 161 has the switch turned on to be connected with the GNDand the output to the transformer 2 becomes a low voltage level output(hereinafter, the “Lo output”). On the other hand, when the PWM outputfrom the control circuit 1514 is the “L output”, the output circuit 161has the switch turned off and the amplitude value (voltage value) of theamplitude control signal of the D/A conversion 1412 becomes the outputto the transformer 2.

With this configuration, the output circuit 161 is capable of outputtingthe control signal that has the frequency of the PWM signal and thevoltage value of the amplitude control signal as the amplitude. Here,FIG. 3 is an example of the configuration of the output circuit 161, andthe output circuit 161 may be configured to make the voltage value ofthe amplitude control signal as the amplitude of the control signal whenthe PWM signal is the “H output”, and make the “Lo output” as theamplitude of the control signal when the PWM signal is the “L output”.That case can also be addressed by the adjustment against the compareregister values to be set to the compare registers 1512 and 1513.

The output circuit 162 may be the same as the output circuit 161. Thatis, the output circuit 162 outputs the control signal for the ultrasonicmotor 3 based on the PWM signal that is output by the control circuit1529 and the amplitude control signal that is output by the D/Aconversion 1422.

The control signals that are output by the output circuit 161 and theoutput circuit 162 have a phase difference of 90 degrees. The phasedifference between the control signals from the output circuit 161 andfrom the output circuit 162 are adjusted by adjusting the compareregister values set to the compare registers 1512 and 1513, 1522 and1523, respectively.

FIGS. 4A, 4B, and 4C show an example of relationships among the D/Aconverting unit 141, the timer 151, and the output circuit 161 inoutputting the signals respectively. The axis of the ordinates shows theoutput states of the respective signals and the axis of the abscissasshows the passage of time. The counter 1511 counts between “000” and“FFF”. To the compare registers 1512 and 1513, the values between “000”and “FFF” are set as the compare register values. Each of the compareregisters 1512 and 1513 compares to see if the compare register valueset thereto matches the count of the counter 1511.

First, at the time a when the set value to the compare register 1512matches the count value, the counter 1511 resets the count value to “0”.When the compare register value set matches the count value of thecounter 1511, the compare register 1512 outputs the pulse control signalto the control circuit 1514. When the pulse width control signal isinput from the compare register 1512, the control circuit 1514 outputsthe PWM signal by the “H output”. When the “H output” of the PWM signalis input, the output circuit 161 outputs the “Lo output” to thetransformer 2 as the control signal.

Next, from the time a to the time b, the control circuit 1514 keeps the“H output” of the PWM signal. Accordingly, the output circuit 161 keepsoutputting the “Lo output” to the transformer 2 as the control signal.

Next, at the time b when the compare register value set matches thecount of the counter 1511, the compare register 1513 outputs the lowlevel signal. When the low level signal is input, the control circuit1514 makes the PWM signal as the “Lo output”. When the PWM signal isinput as the “L output”, the output circuit 161 outputs the amplitudevalue (the voltage α in FIG. 4C) of the amplitude control signal fromthe D/A conversion 1412 to the transformer 2 as the control signal.

Next, from the time b to the time c, the control circuit 1514 keeps the“L output” of the PWM signal. Accordingly, the output circuit 161 keepsoutputting the amplitude value (the voltage α in FIG. 4C) of theamplitude control signal from the D/A conversion 1112 to the transformer2 as the control signal.

Next, at the time c when the set value to the compare register 1512matches the count value, the counter 1511 resets the count value to “0”.When the compare register value set matches the count value of thecounter 1511, the compare register 1512 outputs the pulse control signalto the control circuit 1514. When the pulse width control signal isinput from the compare register 1512, the control circuit 1514 outputsthe PWM signal by the “H output”. When the “H output” of the PWM signalis input, the output circuit 161 outputs the “Lo output” to thetransformer 2.

In that manner, the output circuit 161 can output the control signalthat has the amplitude of the amplitude control signal of the D/Aconversion 1412 from the time a to the time c as one cycle. Similarly,from the time c to the time e is taken as one cycle.

The relationships among the D/A converting unit 142, the timer 152, andthe output circuit 162 in outputting the signals are the same as thosedescribed above. The control signals from the output circuit 161 and theoutput circuit 162 are output with a phase difference of 90 degrees. Forthat purpose, the compare registers 1512 and 1513 in the timer 151 andthe compare registers 1522 and 1523 in the timer 152 achieve the phasedifference by the compare register values set thereto.

Next, the up-down counter 17 receives inputs at the encoded currentrotation direction and the encoded current rotation speed of theultrasonic motor 3 from the encoder 4 and stores them.

Now, the control signal characteristics of the ultrasonic motor 3 andthe correction of the control signal characteristics will be describedwith reference to FIG. 5 and FIG. 6. Each of FIG. 5 and FIG. 6 is adiagram for describing the correction of the control signalcharacteristics of the ultrasonic motor 3. In each graph of FIG. 5 andFIG. 6, the axis of the abscissas shows the frequency and the axis ofthe ordinates shows the amplitude.

The rotation speed of the ultrasonic motor 3 changes as the frequency ofthe control signal is changed. Specifically, the rotation speed of theultrasonic motor 3 becomes faster as the frequency is decreased, and therotation speed of the ultrasonic motor 3 becomes slower as the frequencyis increased. The running torque of the ultrasonic motor 3 changes asthe amplitude of the control signal is changed. Specifically, therunning torque of the ultrasonic motor 3 becomes higher and the rotationspeed becomes faster as the amplitude of the control signal isincreased. On the other hand, the running torque of the ultrasonic motor3 becomes lower and the rotation speed becomes slower as the amplitudeof the control signal is decreased.

As described above, however, the characteristics vary for individualultrasonic motors 3. That is why the ultrasonic motors 3 do notnecessarily have the same rotation speed when they are driven by thecontrol signal with the same amplitude and the same frequency. For thatreason, if the current rotation speed and the current rotation directiondo not match the target rotation speed and the target rotation directionrespectively when the ultrasonic motor 3 is actually driven, then thecharacteristics of the control signal need to be corrected.

It is assumed that the setting frequency and the setting amplitude valueV0 for the target rotation speed β are defined in the ultrasonic motor 3having the characteristics shown in FIG. 5. This means that theultrasonic motor 3 is capable of achieving the target rotation speed βwhen it is driven by the control signal with the frequency a and theamplitude value V0. Referring to FIG. 5, the target rotation speed βwill be achieved by the control signal having the characteristics at thepoint c. The target rotation speed β cannot be actually achieved,however, because the characteristics differ among the individualultrasonic motors 3.

Here, it is assumed that the calculating means 123 calculates thecorrection frequency b and the correction amplitude value V0 from thedifference rotation speed and the difference rotation direction. Thismeans that the target rotation speed β is obtained by the control signalhaving the characteristics at the point d. In that case, thecharacteristics of the control signal can be achieved by only (i.e.,simply) changing the frequency of the control signal from the frequencya to the frequency b.

On the other hand, some characteristics cannot be achieved only bycorrecting the frequency. it is assumed that, in the ultrasonic motorhaving the characteristics shown in FIG. 6, the calculating means 133calculates the correction frequency b and the correction amplitude valueV1 from the difference rotation speed and the difference rotationdirection. This means that the target rotation speed β is obtained bythe control signal having the characteristics at the point d′. In thatcase, for the characteristics of the control signal, not only thefrequency needs to be changed from the frequency a′ to the frequency b′but also the amplitude value V0′ needs to be changed to the amplitudevalue V1.

In the first exemplary embodiment, for the control signals that areoutput by the output circuits 161, 162, the frequencies can be changedby adjusting the compare register values to be set to the compareregisters 1512, 1513, 1522 and 1523, and the amplitude can be changed byadjusting the D/A conversion set values to be set to the D/A conversionregisters 1411, 1421. For that reason, the first exemplary embodiment iscapable of adjusting the characteristics of the ultrasonic motor 3 in awider scope than the case in which the characteristics of the ultrasonicmotor 3 are adjusted only by the frequency of the control signal.

The configuration of the ultrasonic motor control device according tothe first exemplary embodiment has been described above. With thatconfiguration, the ultrasonic motor control device according to thefirst exemplary embodiment is capable of having each of the outputcircuits 161, 162 adjust the amplitude value and the frequency of thecontrol signal based on the amplitude control signal that is output fromeach of the D/A converting units 141 And 142 based on each of the D/Aconversion set values set by the setting means 122 and the PWM signalthat is output from each of the timers 151 and 152 based on each of thecompare register values set by the setting means 122.

The calculating means 123 calculates the differences between the currentrotation speed and the target rotation speed and between the currentrotation direction and the target rotation direction by obtaining thecurrent rotation speed and the current rotation direction of theultrasonic motor 3 that are stored in the up-down counter 17. To correctthe characteristics of the control signal, the calculating means 123calculates the correction frequency and the correction amplitude value.Further, the calculating means 123 calculates the correction compareregister value for generating the correction frequency and thecorrection D/A conversion set value for generating the correctionamplitude value and saves the values in the data storing unit 121. Thesetting means 122 sets the correction compare register values to thecompare registers 1512, 1513, 1522 and 1523, and sets the correction D/Aconversion set values to the D/A conversion setting registers 1411 and1421. Since the output circuits 161 and 162 can output the controlsignals that have the correction frequency and the correction amplitudevalue, the ultrasonic motor 3 can achieve the target rotation speed andthe target rotation direction. Therefore, even if the ultrasonic motor3, which has been the control object, is replaced by another ultrasonicmotor 3 of different characteristics due to exchange or the like, themicrocomputer 1 can achieve the target rotation speed and the targetrotation direction by adjusting the characteristics of the controlsignal.

Since the D/A conversion set value and the compare register value aresaved in the flash memory 12, the correction compare register value andthe correction D/A conversion set value are not lost even when themicrocomputer 1 is switched off. Therefore, when the microcomputer 1 isswitched on again, it can use the ultrasonic motor 3 by using thecorrection compare register value and the correction D/A conversion setvalue.

In addition, since the components of the microcomputer 1 are configuredas the peripheral circuits of the microcomputer 1, they can reduce thepower consumption much more than in the case in which the components areconfigured by using the fixed control circuit.

Further, the setting means 122 and calculating means 123 may beconfigured by hardware, instead of software (the control program)

[Description of Operating Method]

Now, the operating method in the ultrasonic motor control deviceaccording to the first exemplary embodiment will be described withreference to FIG. 7. FIG. 7 shows the operation flow of the ultrasonicmotor control device according to the first exemplary embodiment.

(step 510)

The setting means 122 receives the drive command for the ultrasonicmotor 3 from outside. The setting means 122 determines the settingfrequency and the setting amplitude value corresponding to the targetrotation speed and the target rotation direction included in the drivecommand in the data storing unit 121 of the flash memory 12. The settingmeans 122 obtains the reference compare register value and the referenceD/A conversion set value corresponding to the setting frequency and thesetting amplitude value from the data storing unit 121 of the flashmemory 12.

The setting means 122 writes the reference compare register values inthe compare registers 1512, 1513, 1522 and 1523. The setting means 122also writes the reference D/A conversion set value in the D/A conversionsetting register. The timers 151 and 152 output the PWM signals based onthe reference compare register values.

The D/A converting units 141 and 192 output the amplitude controlsignals based on the reference D/A conversion set values. The outputcircuits 161, 162 output the control signals based on the PWM signal andthe amplitude control signal.

(step S20)

The transformer 2 boosts the voltage of the control signal and outputsthe boosted control signal to the ultrasonic motor 3. The ultrasonicmotor 3 is driven as the control signal is input.

(step S30)

The encoder 4 obtains the current rotation speed and the currentrotation direction of the ultrasonic motor 3. The encoder 4 encodes thecurrent rotation speed and the current rotation direction and outputsthem to the up-down counter 17. The up-down counter 17 stores theencoded current rotation speed and the current rotation direction.

(step S40)

The calculating means 123 obtains the current rotation speed and thecurrent rotation direction that are stored in the up-down counter 17.The calculating means 123 also obtains the target rotation speed and thetarget rotation direction from the setting means 122. The calculatingmeans 123 judges whether the target rotation speed matches the currentrotation speed or not and whether the target rotation direction matchesthe current rot at ion direction or not. If it is judged that they match(i.e., a “Yes”), then the operation proceeds to step S80. On the otherhand, if it is judged that they do not match (i.e., a “No”), then theoperation proceeds to step S50.

(step S50)

If it is judged that they do not match, then the calculating means 123calculates the difference rotation speed and the difference rotationdirection. The calculating means 123 calculates the correction frequencyand the correction amplitude value of the control signal for obtainingthe target rotation speed and the target rotation direction based on thedifference rotation speed and the difference rotation direction. Thecalculating means 123 also calculates the correction compare registervalue corresponding to the correction frequency and the correction D/Aconversion set value corresponding to the correction amplitude value.

The calculating means 123 saves the correction frequency and thecorrection amplitude value in association with the target rotation speedand the target rotation direction as well as the compare register valuein association with the correction frequency and the correction D/Aconversion set value in association with the correction amplitude valuecorrection, respectively, in the data storing unit 121 of the flashmemory 12. The calculation of the correction compare register value andthe correction D/A conversion set value by the calculating means 123 isnot limited to that described above.

The calculating means 123 judges whether the correction for obtainingthe target rotation speed and the target rotation direct ion can beaddressed only by correcting the frequency or not. If it can beaddressed only by correcting the frequency of the control signal (i.e.,a “Yes” in step S50), then the operation proceeds to step S60. On theother hand, if it needs to correct the frequency and amplitude value ofthe control signal (i.e., a “No”), then the operation proceeds to stepS70.

(step S60)

If it can be addressed only by correcting the frequency of the controlsignal (i.e., a “Yes” in step S50), then, the calculating means 123informs the setting means 122 of the judgment result indicating that itcan be addressed only by correcting the frequency. The setting means 122obtains the correction compare register value corresponding to thetarget rotation speed and the target rotation direction from the datastoring unit 121. The setting means 122 writes the correction compareregister values in the compare registers 1512, 1513, 1522 and 1523. Thetimers 151 and 152 output the PWM signals based on the correctioncompare register values. The D/A converting units 141 and 142 output theamplitude control signals based on the D/A conversion set values that iscurrently set. The output circuits 161, 162 output the control signalsbased on the PWM signal and the amplitude control signal. Then, theoperation returns to step S40.

(step S70)

If it needs to correct the frequency and amplitude value of the controlsignal (i.e., a “No” in step S50), the calculating means 123 informs thesetting means 122 of the judgment result indicating that the frequencyand amplitude value need to be corrected. The setting means 122 obtainsthe correction compare register value and the correction D/A conversionset value corresponding to the target rotation speed and the targetrotation direction from the data storing unit 121. The setting means 122writes the correction compare register values in the compare registers1512, 1513, 1522 and 1523. The setting means 122 also writes thecorrection D/A conversion set value to the D/A conversion settingregisters 1411 and 1421. The timers 151 and 152 output the PWM signalsbased on the correction compare register value. The D/A converting units141 and 142 output the amplitude control signal based on the correctionD/A conversion set values. The output circuits 161, 162 output thecontrol signals based on the PWM signal and the amplitude controlsignal. Then, the operation returns to step 540.

(step 580)

When it is judged that the target rotation speed matches the currentrotation speed and the target rotation direction matches the currentrotation direction match, respectively (i.e., a “Yes” in step 540), thecalculating means 123 saves the reference compare register value and thereference D/A conversion set value in the data storing unit 121 of theflash memory 12 as the correction compare register value and thecorrection D/A conversion set value. If the calculating means 123 hassaved the correction compare register value and the correction D/Aconversion set value in the data storing unit 121 at step S60 or stepS70, it does not perform saving processing. Then, the setting means 122performs setting by using the correction compare register value and thecorrection D/A conversion set value.

The operating method of the ultrasonic motor control device according tothe first exemplary embodiment has been described above. As describedabove, the calculating means 123 calculates the differences between thecurrent rotation speed and the target rotation speed and between thecurrent rotation direction and the target rotation direction byobtaining the current rotation speed and the current rotation directionof the ultrasonic motor 3 that are stored in the up-down counter 17. Tocorrect the characteristics of the control signal, the calculating means123 calculates the correction frequency and the correction amplitudevalue.

Further, the calculating means 123 calculates the correction compareregister value for generating the correction frequency and thecorrection D/A conversion set value for generating the correctionamplitude value and saves the values in the data storing unit 121. Thesetting means 122 sets the correction compare register values to thecompare registers 1512, 1513, 1522 and 1523, and sets the correction D/Aconversion set values to the D/A conversion setting registers 1411 and1921. Since the output circuits 161 and 162 can output the controlsignals that have the correction frequency and the correction amplitudevalue, the ultrasonic motor 3 can achieve the target rotation speed andthe target rotation direction. Therefore, even if the ultrasonic motor3, which has been the control object, is replaced by another ultrasonicmotor 3 having different characteristics due to exchange or the like(e.g., manufacturing variations, etc.), the microcomputer 1 can achievethe target rotation speed and the target rotation direction by adjustingthe characteristics of the control signal.

Since the D/A conversion set value and the compare register value aresaved in the flash memory 12, the correction compare register value andthe correction D/A conversion set value are not lost even when themicrocomputer 1 is switched off. Therefore, when the microcomputer 1 isswitched on again, it can use the ultrasonic motor 3 by using thecorrection compare register value and the correction D/A conversion setvalue.

Second Exemplary Embodiment

Now, the second exemplary embodiment will be described with reference toFIG. 8. FIG. 8 is a block diagram show in a configuration of theultrasonic motor control device of the second exemplary embodiment. Theultrasonic motor control device of the second exemplary embodiment isconfigured somewhat similarly the ultrasonic motor control device in thefirst exemplary embodiment. Therefore, the description of the parts thatare the same as those in the first exemplary embodiment will be omittedand the parts different from those in the first exemplary embodimentwill be mainly described.

The ultrasonic motor control device of the second exemplary embodimentdiffers from that of the first exemplary embodiment in the D/Aconverting unit 143 of the microcomputer 1. In the first exemplaryembodiment, the microcomputer 1 has the D/A converting unit 141 foroutputting the amplitude control signal to the output circuit 161 andthe D/A converting unit 142 for outputting the amplitude control signalto the output circuit 162.

In the second exemplary embodiment, the microcomputer 1 has only the D/Aconverting unit 143 for outputting the amplitude control signals to bothof the output circuit 161 and the output circuit 162. The D/A convertingunit 143 has the D/A conversion setting register 1431 and the D/Aconversion 1432. The D/A conversion setting register 1431 may be thesame as the D/A conversion setting registers 1411 and 1422. The D/Aconversion 1432 may be the same as the D/A conversion 1412 and 1422.Therefore, the description functions of the D/A conversion settingregister 1431 and the D/A conversion 1432 will be omitted.

The amplitude values of the control signals output by the outputcircuits 161, 162 usually have the same voltage level. By takingadvantage of that point, in the second exemplary embodiment the D/Aconversion 1432 outputs the amplitude control signal to both of theoutput circuit 161 and the output circuit 162. Therefore, the amplitudevalues of the control signals output by the output circuits 161, 162have the same value.

Accordingly, the power consumption of the microcomputer 1 can be reducedand an effect of reducing heat in the structure can be achieved.

The present invention has thus been described. According to the presentinvention, the microcomputer 1 can adjust the frequency and amplitude ofthe control signal for the ultrasonic motor 3 by adjusting the D/Aconversion set values to be set to the D/A conversion setting registers1911, 1421 and 1431 and the compare register values to be set to thecompare registers 1512, 1513, 1522 and 1523. Accordingly, adjusting thecharacteristics of the ultrasonic motor 3 can be widely performed sothat the ultrasonic motor 3 can be controlled by absorbing the change inthe characteristics due to the exchange, manufacturing variations,service life deterioration or the like of the ultrasonic motor 3.

Since the D/A conversion set value and the compare register value thatare required for adjusting the control signal, are saved in the flashmemory 12, the correction compare register value and the correction D/Aconversion set value are not lost even when the microcomputer 1 isswitched off. Therefore, when the microcomputer 1 is switched on again,it can use the ultrasonic motor 3 by using the correction compareregister value and the correction D/A conversion set value.

In addition, since the components of the microcomputer 1 are configuredas the peripheral circuits of the microcomputer 1, they can reduce thepower consumption much more than in the case in which the components areconfigured by using the fixed control circuit.

Furthermore, as shown in FIG. 9, the ultrasonic motor control device maybe installed in various products (a product 200 in FIG. 9), for example,cameras, vehicles, etc. with great benefit.

Although the invention has been described above in connection withseveral exemplary embodiments thereof, it will be appreciated by thoseskilled in the art that those exemplary embodiments is provided solelyfor illustrating the invention, and should not be relied upon toconstrue the appended claims in a limiting sense.

Further, it is noted that, notwithstanding any claim amendments madehereafter, applicant's intent is to encompass equivalents all claimelements, even if amended later during prosecution.

1. A microcomputer that outputs a pulse signal controlling an ultrasonicmotor, the microcomputer comprising: a digital/analog, D/A, conversionset register that stores a D/A conversion set value setting an amplitudevalue of the pulse signal; a D/A converter that generates the amplitudevalue based on the D/A conversion set value; a first compare registerthat stores a first compare register value setting a frequency of thepulse signal; a second compare register that stores a second compareregister value setting a duty ratio of the pulse signal; a counter thatoutputs a count value; a first comparator that compares the firstcompare register value with the count value to generate a firstcomparison result signal; a second comparator that compares the secondcompare register value with the count value to generate a secondcomparison result signal; and an output circuit that generates the pulsesignal based on the amplitude value, the first comparison result signaland the second comparison result signal.
 2. The microcomputer accordingto claim 1, further comprising: a central processing unit, CPU, that iscoupled to the D/A conversion set register, the first compare registerand the second compare register, wherein the CPU monitors a rotationspeed of the ultrasonic motor that is driven in response to the pulsesignal that is generated based on the D/A conversion set value, thefirst compare register value and the second compare register value, andcorrects, based on a monitoring result, at least one of the D/Aconversion set value, the first compare register value and the secondcompare register value.
 3. The microcomputer according to claim 2,wherein the microcomputer is coupled to an encoder that obtains acurrent rotation speed of the ultrasonic motor, and further comprises:an up-down counter that is coupled between the CPU and the encoder, andthat receives information of the current rotation speed of theultrasonic motor, and wherein the CPU monitors the rotation speed of theultrasonic motor by the information.
 4. The microcomputer according toclaim 1, further comprising: a storage unit that stores the D/Aconversion set value, the first compare register value and the secondcompare register value, wherein the D/A conversion set value allows fordetermining the amplitude value of the pulse signal corresponding to atarget rotation speed that is targeted by the ultrasonic motor, whereinthe first compare register value allows for determining the frequency ofthe pulse signal corresponding to the target rotation speed that istargeted by the ultrasonic motor, and wherein the second compareregister value allows for determining the duty ratio of the pulse signalcorresponding to the target rotation speed that is targeted by theultrasonic motor.
 5. The microcomputer according to claim 1, wherein themicrocomputer respectively comprises the D/A conversion set register,the D/A converter, the first compare register, the second compareregister, the counter, the first comparator, the second comparator, andthe output circuit in a number corresponding to a number ofpiezoelectric bodies in the ultrasonic motor.
 6. The microcomputeraccording to claim 1, wherein the microcomputer respectively comprisesthe first compare register, the second compare register, the counter,the first comparator, the second comparator, and the output circuit in anumber corresponding to a number of piezoelectric bodies in theultrasonic motor, and wherein the D/A conversion set register and theD/A converter are shared.
 7. A product comprising: the microcomputeraccording to claim 1; and the ultrasonic motor that is coupled to themicrocomputer.
 8. A product comprising: the microcomputer according toclaim 3; the ultrasonic motor that is coupled to the microcomputer; andthe encoder that is coupled between the microcomputer and the ultrasonicmotor.